Current voltaic cells and solar panel systems have limited efficiency and require complex materials resulting in significant associated costs. Many solar panels use wafer-based crystalline silicon cells or cadmium or silicon-based thin-film cells. These cells are fragile and must be protected from moisture through adding multiple protective layers. Panels are deployed in series for increased voltage and/or in parallel for increased current. Panels are interconnected through conducting metallic wires. An inherent problem with common systems is the susceptibility of the cells to overheat due to reverse current flow when a portion of the panel is shaded and another portion of the panel is in direct sunlight. Another inherent problem is that solar cells become less efficient at higher temperatures, which limits the geographical effectiveness of light conversion to electricity. Improvements such as arrayed lenses and mirrors improve the focusing of light to increase efficiency but have higher fabrication complexity and associated costs.
Dye-sensitized solar cell (DSSC) is a solar cell technology based on semiconducting material placed between a light-sensitized anode and an electrolyte. Fabrication of DSSCs is not cost-effective and requires expensive materials such as platinum and ruthenium. Additionally, DSSC stability is a concern, as there exists a climate-related sensitivity of the liquid electrolyte.
Quantum dot solar cell (QDSC) technology is based on dye-sensitized solar cells but utilizes low band gap semiconductor nanoparticles, also known as quantum dots, which include CdS, CdSe, Sb2S3, PbS and other metalloid salts as light absorbers. The advantages of quantum dots are that band gap preferences are dictated by particle size and that they offer high extinction coefficients. The efficiencies of QDSCs are still low with over 5% demonstrated for both liquid junction and solid-state cell types and the fabrication costs are still prohibitive.
Polymer (and copolymer) solar cells are made from thin films of organic semiconducting polymers such as polyphenylene vinylene and copper phthalocyanine. These cells differ from the aforementioned inorganic solar cells because they do not require a built-in electric field of P—N junctions to separate electrons from holes. Instead, organic cells contain an electron donor and an electron acceptor. In a polymeric solar cell, the electron donor is excited by a photon, the energy of which is converted to an electron and hole pair. The pair diffuses to the donor-acceptor interface whereby the electron and hole are separated and current is generated.
Existing photovoltaic panels produce electricity from a range of wavelengths of light but cannot harness wavelengths in the ultraviolet and infrared ranges (except for recent conceptual studies with polymeric and copolymeric solar panels, although these efficiencies remain low at 3-4%). The available panels also produce little electricity from low light or diffuse light. Increased effort in design concepts split light into monochromatic wavelengths and to direct these wavelengths to different solar cells specifically tuned to those wavelengths and are projected to increase the efficiency by up to 50%, but require significant technical advances and are very costly.
Field experiments involving solar panel technology reveal that a drop of 1.1% in peak output occurs for every increase in degrees Celsius past a threshold temperature of 42-44 degrees Celsius. This is problematic as on hot and sunny days, the surface temperature of a panel can exceed 90 degrees Celsius and can often experience localized heat buildup within the panel causing spots to be as high as 800 degrees Celsius due to the reflective layering needed in current solar panels. Cold and sunny environments are the optimal conditions for maximal efficiency of the current solar panels.
Photovoltaic solar panels have been used since the 1950s for the conversion of sunlight to electricity, and decades of technological advancements have only increased the efficiency to 12-28.8%. Recently, significant nanotechnological advancements have been made to increase the efficiency from 10% to almost 29% but at increased design complexity and fabrication cost.